The invention relates to light element with a translucent surface, and more particularly, to a light element that efficiently extract the direct as well as the diffuse portion of the optical radiation impinging on the translucent surface.
Sunlight shining through windows, glass walls and roofs can be used to illuminate the interior of a room. However, a strong light intensity can oftentimes cause glare, an inhomogeneous light distribution as well as a severe temperature increases in the interior space. Conversely, blinds can block the light flux from reaching the building interior so that artificial lighting has to be provided. The light reaching the interior space consists of sunlight, which enter directly from the outside areas, and uniformly distributed diffuse light that is hemispheric, i.e. radiated from all directions into the half space. The intensity of the diffuse light can reach up to 10% of the direct light depending on the atmospheric conditions.
Because of the need to provide shade, a major portion of the electric power in many high-rise buildings is consumed during the day as a consequence of the energy consumed by lamps and light fixtures installed in the interior spaces. Artificial light sources can be characterized as “heating elements with a weak illumination effect,” requiring additional electrical energy for air conditioning to remove the generated heat from the interior space.
Several types of blinds have been developed over the years wherein their relative orientation relative to the sun can be controlled so that the blinds are either transparent or reflecting. These blinds can reflect the unwanted direct light from the outside and only let the diffuse light pass. For example, blinds can be made of rotatable prisms. The transparent prism systems reflect the direct sunlight and let the diffuse light pass if they are oriented perpendicular to the sun rays, thereby forming selectively transparent blinds.
These conventional systems can improve the illumination of interior spaces with windows, glass facades or glass roofs. However, the masked-off direct sunlight—although valuable as an energy source—is disadvantageously returned to the outside through reflection.
It would therefore be desirable and advantageous to provide an improved light element that obviates prior art shortcomings and that can efficiently utilize the radiation directly impinging on the translucent surface.